This invention relates to a system of acquiring and displaying information corresponding to the time history of a variable analog value.
The Emschermann et al U.S. Pat. No. 3,880,007 discloses a temperature-sensitive unit operative for generating an analog temperature indicating electrical signals and is adapted to operate in very high temperature environments. As is disclosed in the aforementioned patent, a number of techniques have been employed in the prior art to obtain temperature readings in a high temperature environment. As noted, for registering apparatus which is electro-mechanical, its energy consumption can be very high and may serve to cause very fast temperature build-ups inside heat-insulating container. It is also known to position the recording instrumentality externally of the hostile environment and to connect same to the temperature-sensitive element by means of lengthy wires. Further, it is also known to provide a radio transmitter to transmit a temperature-indicating radio signal and to recover same externally of the hostile environment and, finally, it is also known to link the temperature-sensitive element and the remotely located measuring and recording equipment by optical means.
The aforesaid patent discloses a system in which the output of a binary counter is connected to a plurality of constant current sources, the current sources preferably being capable of supplying increasing current to the reference resistor.
When the voltage drop across the reference resistor is less than that across the temperature-sensitive resistor, the binary counter may be clocked to bring the two voltage drops into coincidence. In one embodiment, illustrated in FIG. 3, a binary store accepts successive values of the binary counter count which represent temperatures higher than the reference temperature.